Ok. I got the impression that it was to be run from the RPi itself.
BTW: I got the bcm2835-rng idea from https://github.com/debian-pi/raspbian-ua-netinst/blob/v1.1.x/scripts/etc/init.d/rcS#L234
The project is unfortunately a bit outdated (installs Jessie), but it starts gathering entropy with RPi's HWRNG quite early and then starts a complete installation process, which in itself generates a lot of entropy (afaiui).
You can customize the installation (config file + scripts), including generating keys at the end of the installation.